Sirleaf, Africa's first democratically
elected female president, shared the award with
women's rights campaigner Leymah Gbowee, also from Liberia, and Tawakkul
Karman, a female icon of the protest movement in Yemen.

The peace prize was announced in
October, along with the Nobel awards for
medicine, physics, chemistry, literature and economics. Worth 10 million kronor
($1.5 million) each, the Nobel Prizes are always handed out on the anniversary
of award founder Alfred Nobel's death on Dec.
10, 1896.

By selecting Karman, the prize
committee recognized the Arab Spring movement that has toppled autocratic
leaders in North Africa and the Middle East. Praising Karman's struggle against
Yemen's regime, Nobel committee chairman Thorbjoern Jagland also sent a message
to Syria's leader Bashar Assad, whose crackdown on rebels has killed more than
4,000 people according to U.N. estimates.

A security check is performed on the stage at the Stockholm Concert Hall which will host the Nobel Prize ceremony in Stockholm, Saturday, Dec. 10, 2011. The Nobel Day takes place Saturday and will begin with the traditional Nobel Prize award ceremony at the Stockholm Concert Hall, where the Laureates will be presented in speeches by members of the respective Nobel Committees. (AP Photo/Matt Dunham)

"President Assad in Syria will not
be able to resist the people's demand for freedom of human rights,"
Jagland said.

Karman is the first Arab woman to win
the prize and at 32 the youngest peace laureate ever. A journalist and founder
of the human rights group Women Journalists without Chains, she also is a
member of the Islamic party Islah.

Wearing headphones over her Islamic
headscarf, she clapped and smiled as she listened to a translation of Jagland's
introductory remarks.

In her acceptance speech, Karman paid
tribute to Arab women and their struggles "in a society dominated by the
supremacy of men."

According to an English translation of
her speech, delivered in Arabic, she criticized the "repressive,
militarized, corrupt" regime of outgoing President Ali Abdullah Saleh. She
also lamented that the revolution in Yemen hasn't gained as much international
attention as the revolts in Egypt, Tunisia, Libya and Syria.

"This should haunt the world's
conscience because it challenges the very idea of fairness and justice,"
Karman said.

No woman or sub-Saharan African had won
the prize since 2004, when the committee honored Wangari Maathai of Kenya, who
mobilized poor women to fight deforestation by planting trees.

Sirleaf, 73, was elected president of
Liberia in 2005 and won re-election in October. She is widely credited with
helping her country emerge from an especially brutal civil war.

The Nobel chairman noted that she
initially supported Charles Taylor but later dissociated herself from the
former rebel leader who is now awaiting judgment from the International
Criminal Court on charges of war crimes in Sierra Leone.

Gbowee, 39, challenged Liberia's
warlords as she campaigned for women's rights and against rape. In 2003, she led
hundreds of female protesters through Monrovia to demand swift disarmament of
fighters, who continued to prey on women, despite a peace deal.

"We used our pains, broken bodies
and scarred emotions to confront the injustices and terror of our nation,"
she told the Nobel audience in Oslo's City Hall.

She called the peace prize a
recognition of the struggle for women's rights not only in Yemen and Liberia,
but anywhere that women face oppression.

"We must continue to unite in
sisterhood to turn our tears into triumph," Gbowee said. "There is no
time to rest until our world achieves wholeness and balance, where all men and
women are considered equal and free."

This year's prize generated less
controversy than the 2010 award, which went to
imprisoned Chinese dissident Liu Xiaobo, infuriating China's leadership. Xiaobo
was represented by an empty chair at the award
ceremony.

The other Nobel Prizes - in medicine,
chemistry, physics and literature, and the Nobel Memorial Prize in Economic
Sciences - were presented by Swedish King Carl XVI Gustaf at a separate
ceremony Saturday in Stockholm.

In an emotional moment, Claudia
Steinman accepted the Nobel diploma and medal on behalf of her husband,
Canadian-born Ralph Steinman, who died of cancer just days before the medicine
prize was announced on Oct. 3. Before sitting down, she blew a kiss toward the
ceiling of Stockholm's Concert Hall.

An exception was made to Nobel rules
against posthumous awards because the jury
wasn't aware of Steinman's death when it tapped him to share the award with American Bruce Beutler and French scientist
Jules Hoffman for discoveries about the immune system.

The typically stiff white-tie crowd
erupted in cheers when wheelchair-bound Swedish poet Tomas Transtromer,
partially paralyzed by a stroke two decades ago, received the Nobel Prize in
literature. The 80-year-old had figured in Nobel speculation for so many years
that even his countrymen had started to doubt whether he would ever win.

U.S.-born scientists Saul Perlmutter,
Brian Schmidt and Adam Riess collected the physics prize for discovering that
the universe is expanding at an accelerating pace.

The chemistry award
went to Israel's Dan Shechtman for his discovery of quasicrystals, a
mosaic-like chemical structure that researchers previously thought was
impossible.

Americans Christopher Sims and Thomas
Sargent won the economics prize for describing the cause-and-effect
relationship between the economy and government policy.